Carton based packages for liquid food products are well known in most parts of the world. For instance, Tetra Brik® packages are used in many parts of the world for milk, juice and other beverages. There are several reasons why carton based packages have gained such popularity. The environmental benefits of the packages, e.g. that the packages are to a large extent is produced by renewable material, and the efficient logistics of brick shaped packages, are some examples to this popularity and also a reason why consumers today choose carton based packages instead of plastic bottles. Another reason why carton based packages are popular is that the filling machines producing the packages are cost efficient compared to other alternatives and that the total cost for running a carton based filling machine is very competitive.
There are generally two different types of filling machines for carton packages, blanks fed packaging machines and roll fed packaging machines. For blanks fed packaging machines, blanks, being pieces of packaging material with two ends welded together such that a folded sleeve is formed, are fed to the filling machine, erected into an open sleeve, folded and sealed such that bottoms are formed, filled with product and sealed and folded such that a package filled with product is achieved. For roll fed packaging machines a tube is formed from a web of packaging material by continuously directing the web and making a longitudinal sealing. The tube is filled with product and then by making successive transversal sealings and cuttings in a lower end of the tube, packages are formed. By providing means for holding the tube in position during the transversal sealing and cutting, and by providing subsequent folding means different forms may be obtained.
In order to do the transversal sealing, sometimes also referred to as non-continuous sealing, different technologies can be used. A today commonly used technology is so-called induction heat sealing, or sometimes only induction sealing. The general principle of this technology is to induce a current in an Aluminum foil in the packaging material such that heat is generated and as an effect of this that plastic layers in the packaging material melt at the same time as two different sides of the packaging material are pressed together such that the sealing, or sometimes also referred to as welding, is achieved. If the packaging material does not comprise Aluminum foil different technologies are used, such as ultrasonic sealing in which ultrasound is used for melting the plastic layers such that a sealing can be achieved.
A sealing device for induction sealing usually comprises a support body, at least one conductive element, e.g. a coil, held in the support body and a magnetic insert, sometimes referred to as magnetic field concentrator (MFC), placed in the support body next to the conductive element in order to provide for that the electromagnetic field is directed towards the packaging material, such that a more efficient sealing is achieved.
Even though induction sealing devices have been used for a long time there is still a need to improve these in terms of wear resistance, both due to the forces used when providing the pressure, but also due to e.g. hydrogen peroxide or other chemical used for sterilizing the package material, and to be able to produce the inductors in a cost efficient manner.